librem5-cameras.udev: Handle module (un)loading a bit more gracefully

This makes it unload camera modules when rfkill is blocked (either hard
or soft) and load it back when it's getting unblocked. Makes apps like
Millipixels handle engaged killswitch a bit better (at least unless the
switch is engaged while a camera is in use).
6 jobs for cam in 5 minutes and 23 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed shellcheck #376105
librem5

00:00:08

 
  Package
passed package-pureos-byzantium #376106
librem5

00:00:49

passed package-pureos-byzantium:arm64 #376107
librem5:arm64

00:02:01

 
  Test Package
passed autopkgtest-pureos-byzantium-package #376110
librem5

00:03:12

passed lintian-pureos-byzantium-package #376109
librem5

00:00:51

failed autopkgtest-pureos-byzantium-package #376108
librem5

00:00:21